I have a 1992 Isuzu Rodeo LS 4x4 3.1 litre V6 with the 4L30E auto trans. For a while I'd been having issues with the mode switch as per usual with this transmission & moving it through the gears with the key off then starting it in neutral solved the problem until the switch itself came loose causing the trans to shift wildly and even pop in and out of neutral over and over, etc. Knowing what had to be done I pulled the switch, took it apart & cleaed it re-greasing it with electrical grease (the type you put in/on your tailight bulbs to prevent corrosion).

I replaced the switch adjusting it as per the manual suggests and after a little trial and error the switch and transmission started working like new again shifting perfectly. That is, until you drove it for about 20 minutes or so then again with it shifting through the gears without my doing anything before finally popping into neutral where it would stay until I put the shift lever in 1st then it would re-enguage, and sometimes work OK again for a while until you came to a stioplight or stop sign and had to stop the vehicle. Then it would start messing up again shifting mostly only from 1st to 2nd but after coaxing it would eventually go through the rest of the gears, then pop into neutral and do this again over and over.

Well, knowing it had been about 40,000 since it's last fluid/filter change I figured the fluid might be breaking down due to heat after 20 minutes of driving so I decided to change the fluid/filter. This time though I elected to do it myself due to lack of cash and, well, if you have seen the underside of one of these things you know what I went through just to get the main pan off of the transmission -removal of about 3 rock/splash/heat guards & secondary crossmember guard where 90 % of the bolts broke off flush, and then removing the main rear crossmember holding the rear motor mount breaking all but 2 bolts there, removal of the mount, and to top all of that off I had to use my saws all to cut the Y pipe crossing under the main pan (it has two) where the filter is.

Long story short, I changed the fluid and filter, drilled and re-tapped enough threads to get the main rear crossmember back on that holds the rear motor mount, leaving the guards off I took it for a test drive (very loud w/o Y pipe). Transmission shifted fine for the 6 miles into town, then fine again after stopping for gas and for another 4 miles where I stopped at a store 5,6 miles from home to get something I'd forgotten. 10 minutes later I re-start the vehicle no check trans light and started home. Well, Trans only shifted from first to second gear -I only had first and second gear for the 5 miles home no matter how much I slowed down, nor how fast I went (up to 50 or so in 2nd) or tried to coax it as I did before fluid/filter change. However when I sped up to try and get it to shift, instead of shifting it would pop into neutral until I slowed down and moved the shifter now only into 3rd to get to re-enguage (before fluid change had to shift to 1st for it to re-enguage).

What could be causing the transmission to shift fine for the first 15-20 minutes or so of driving then mess up and shift only from 1st to 2nd afterward. Once I let it cool down for an hour it shifted fie again for about 15 miutes?

This is very wierd symptoms for me. While I had pans off checked them with paper towels for metal shavings and found none. Trans looks new inside. It was replaced in 2006 with a new, not rebuilt or re-conditioned, new transmission. That's how I knew how long the fluid had been in there. So in reality, this transmission only has around 38-40,000 miles on it.

I apologize for the lengthy explanation but I wanted to post a clear detailed description of what it is doing.

Any ideas or suggestions would be appreciated. I love the truck and otherwise it runs perfecy despite the high milage on engine. Could there be a short in the wiring going to the transmission or maybe something wrong in the ECM?

The mode switch inside didn't look so great but I cleaned it with electronics cleaner and 2000 grit wet/dry paper (dry, of course) and made sure the spring and ball bearing went together right as I re-assembled it. But if this switch works OK while cold, could it be malfunctioning after 20 minutes of driving when things get hot?

I don't know. I thank you in advance for any suggestions any of you can provide. Also, Happy to have found this forum and happy to be here!

 

Well i looked online for a while to try to find a problem with your 4L30E Transmission. Its a gm tranny and i know they suck really bad. Ever since they went electronic they were horrible. Everyone knows Chevy has bad electronics. So idk if you were referring to the Range/Mode selector that you replaced. Sounds like that could be one thing. Another can be a shift solenoid on the tranny. Maybe your transmission is in limp mode? Also if the alternator is not putting out the right voltage that can screw with the tranny too.

Let me know i will try and help you with your problem.

 

I appreciate the reply. Replaced the mode switch again today with a different one and still same problem. It shifted fine for the first 5-6 miles then again with only 1st and 2nd.

I'm disabled and cannot continue this type of physical work. I'm paying for it painfully. Therefore, though I love my Rodeo I have decided to buy something else near the end of this month when I get paid again, and put my Rodeo up for sale for $7-800 or so neg.

It's definately worth that as it has ice cold air (important when you live in Florida) and many many new parts such as master cylinder, etc, and also has those rare factory mag wheels with the zero offset and wider width so you can run the 10-31 LT rubber.

I have a 21 foot bass boat I pull around once in a while (my Rodeo pulls this well, you forget it's back there) but usually not very far (less than 3 miles to ramp). I seriously doubt this had anything to do with current transmission problem, but I'm going to buy a bigger truck with a 4.0 or larger v6 or a v8.

I've been looking at Dodge Durango's and Ram 4x4 trucks as they are within my doable (low) price range and will easily pull my boat. However I might just buy something old enough to not have all the electronic crap on cars these days so the average person can fix things easily. I can't afford to pay a mechanic every time something goes wrong due to my again (low) fixed income.

Again I thank you for your reply. If you or anyone does come up with a solution to fix my Rodeo I will still give it a try until I either sell it or get something else. Right now I can only depend on it to get me to the convenience store a mile down the road & they hardly have any stock (things you need from them) in.

 

Well sorry its not an easy fix. But if you are getting a new rig you should get a 99 rodeo with the 3.2 DOHC 5spd. It has 205HP and it moves. It runs great with 150K and gets about 19MPG half city half highway. Plus with a 5spd you wont have weird tranny problems. The only problem i have now is the FTP sensor is messed up on the tank.

 

I have been having the same problem exact problem and you can read about it and it can be a lot of things. i wish i could find the answer to it. Goes into safe/limp mode. Now we have pretty much narrowed it down to an open wire coming from the TCM (code 37) which makes sense because its once the vehicle is hot that the issue occurs. That tells me the wire in question is somewhere that gets hot, pretty much the whole truck. So i know that the situation is I should check all the wires running from the tcm but of course i dont know where they go and i dont have a lift...i was thinking of buying the shop manual for the truck but i doubt it has the physical path of the wiring. i have the schematics of which circuits connect to what but that doesnt mean i know where the wires disappear to after they leave the under dash area....they go lots of places. Its going to be a time consuming process for me i guess. Any suggestions appreciated. Generally the airbag light is on also.
Mine is the 3.2 DOHC engine 4wd Limited version

 

I never did find the problem. About a week after my last post I found something I've been wanting for years: a cherry jet black Dodge Ram 2500 V10 4X4 Ext. Cab Long Box with a 4" lift running 37's on 17 x10 inch Dick Cepec DC1's. Truck has a rebuilt trans mission and it's the 47RE HD (heavy duty) auto trans with lockup converter. To get this truck that looks this good I had to by it needing an engine. I found a certified 144,000 mile V10 on ebay which is now sitting in my truck and it runs like a new one. Trans shifts like a new one, and overall I'm very happy as it pulls my boat with ease. The V10 has lots of horsepower and is a far far different driving experience than my Rodeo was.

I would still like to find another Ropdeo as a second vehicle but I garantee this, it will be a standard transmission model. I've included a photo of my new Dodge.

I thank everuyone for your replies and ideas. It just became too difficult for me in my current physical condition to continue working on the transmission.